Surface Based Underwater Communications

Abstract

In an underwater environment signal propagation for the acoustic channel is subject to major multipath effect. Therefore, most underwater communication schemes require that the position of the transmitter or receiver is fixed while using directional antennas in order to ensure high signal-tonoise ratio. However, such a requirement hinders node discovery and ad-hoc formation of underwater networks and restraints communication between autonomous underwater vehicles (AUVs) where node locations change over time. This paper proposes a novel approach to underwater communications by relying on the water surface to establish communication links. The proposed surface-based reflection (SBR) model works by requiring the transmitting node to direct its energy towards the water surface. The receiver then applies homomorphic deconvolution techniques to determine the channels impulse response used in obtaining the reflected signal. The receiver is then able to determine the location of the transmitter by triangulating the transmitted and reflected signals with respect to the water surface. Simulation experiments are provided to validate the SBR approach.

Surface-Reflection-Based Communication and Localization in Underwater Sensor Networks

“…In addition, SBR utilizes both LOS and NLOS links to fully utilize the spatial spectrum. In addition to the simulated results presented in Emokpae and Younis [2010], in this article we provide empirical results that validate the proposed SBR scheme in a controlled tank.…”

“…(17) implies that TL RBR > TL RSR , which is common in underwater acoustics as we explained in Section 3 when we analyzed the multipath transmission loss. A detailed description of the SBR recovery process (i.e., recovery of h r [n]) can be found in Emokpae and Younis [2010]. Figures 10 through 13 give an illustration of the channel IR recovery process of SBR in a controlled tank.…”

“…Furthermore, it has been shown in Emokpae and Younis [2010] that the relative mobility between a transmitter and receiver has little effect on the recovery of the channel IR h r [n] when the transmitted signal is not modulated by a single carrier frequency. It has been also shown that the homomorphic deconvolution mechanism used to recover the channel IR h r [n] will resolve all multipath components of the channel, regardless of the transmitter-receiver geometry.…”

Surface Based Anchor-Free Localization Algorithm for Underwater Sensor Networks

“…Thus, for a known surface function , , the receiver will be able to determine the reflected vector as shown in (3). A homomorphic deconvolution process is also provided in [10] for the receiver to recover the RSR eigenray. In this paper, we presents an approach for determining , , which is assumed to be known in [10].…”

“…To overcome the limitations of present systems, this paper employs the surface-based reflection (SBR) scheme [10], which uses the reflections from the water surface to establish communication links. The receiver only accepts signals that are reflected at the surface by checking the RSS and comparing it to the calculated reflection coefficients.…”